This invention relates to a technology for a computer system composed of a host computer, a storage system, and a management computer. More particularly, this invention relates to a technology of setting an environment for backing up data that is requested to be written by an application.
In a common computer system with a host computer, a storage system, which stores data requested to be written by the host computer in volumes, and a management computer, a loss of data stored in a volume may happen due to damage to the storage system from a disaster, a physical failure resulting from, for example, the expiration of the service life of a disk drive in the storage system, destruction of data stored in a volume by a computer virus, a user's wrong operation, and the like.
The computer system prepares for such data loss by periodically backing up data stored in the volumes so that the data can be restored if destroyed.
Data stored in a volume can be backed up by “local backup” in which a local copy function is used to back up the data to another volume in the storage system that has the volume to be backed up, or by “remote backup” in which the data in the volume to be backed up is copied (mirrored) by a remote copy function to a volume in another storage system, and then backed up by a local copy function within this other storage system.
Remote backup is capable of preventing data loss when data stored in a volume in one of storage systems is destroyed by a disaster or the like. Disasters include man-made disasters such as power failures and fires, and natural disasters such as earthquakes, eruptions, and typhoons.
With remote backup which stores backup data in another storage system far apart from the original storage system, when a disaster strikes the original storage system, the backup data stored in the other storage system which is not affected by the disaster is available for use. A user can thus avoid data loss from a disaster.
The site of a storage system that has a volume whose data is to be backed up is called a “local site” whereas the site of a storage system to which the data is backed up by remote backup is called a “remote site”.
When a user's wrong operation or the like causes logical destruction of data and the task is to be resumed with the use of data stored on the remote site, the resumption of the task takes long because the data is restored by remote copy between storage systems.
A technology of speeding up restoration using remote backup is disclosed in JP 2003-242011 A. According to this technology, one or more generations of backup data is stored on the remote site and on the local site as well. In the case where data to be restored is found on the local site at the time of restoration, the data is restored by local copy. In the case where the data to be restored is found only on the remote site at the time of restoration, on the other hand, the data is restored by remote copy from the remote site.